Interface‐Engineered Li–Ni–O/Ni Heterostructures With Tunable Vacancies on Biochar Enable Biomass‐to‐Hydrogen Conversion

ABSTRACT Efficient biomass steam reforming for hydrogen production is challenged by steam activation limits and catalyst deactivation. Here, we report Li‐promoted Ni‐ and Co‐based biochar catalysts that achieve significantly enhanced hydrogen yields at 600°C, with a stronger effect on Ni than Co. Among 16 representative promoters, NiLi‐biochar delivers 1.3–2 times higher H 2 yields. This superior performance is attributed to the formation of a Li–Ni–O/Ni heterostructure enriched with oxygen vacancies and strong base–weak acid sites. Density functional theory reveals that the Li–Ni–biochar interface forms an interfacial polar field and facilitates electron density redistribution, which could lower the energy barrier for H 2 O dissociation and stabilize intermediates. The synergistic regulation of Li content, steam‐to‐carbon ratio, and steam reaction time tunes catalyst structure and reactivity. This work unveils the intrinsic electron function of lithium at the metal–carbon interface and offers a sustainable strategy for designing low‐cost, high‐performance reforming catalysts.